When a liquid-based Pap smear is performed, a biological specimen sample (cellular material) is obtained from the patient, from which a specimen slide is prepared. The specimen slide is then evaluated, e.g., by a cytotechnologist, and typically classified by the cytotechnologist as either “normal” or “abnormal.” An abnormal sample normally falls in one of the major categories defined by The Bethesda System for Reporting Cervical/Vaginal Cytologic Diagnosis, which categories include Low-Grade Squamous Intraepithelial Lesions (LSIL), High-Grade Squamous Intraepithelial Lesions (HSIL), Squamous Cell Carcinoma, Adenocarcinoma, Atypical Glandular cells of Undetermined Significance (AGUS), Adenocarcinoma in situ (AIS), and Atypical Squamous Cell (ASC), which can be further sub-divided into Atypical Squamous Cell, cannot exclude HSIL (ASC-H) and Atypical Squamous Cell of Undetermined Significance (ASC-US).
A specific Human Papilloma Virus (HPV) deoxynucleic acid (DNA) test, referred to as the Hybrid Capture II HPV DNA assay, manufactured by Digene Corporation, has been used to determine whether patients, whose Pap smears have been classified as ASC-US, have HPV. Based on the strong correlation between HPV and cervical cancer, it has been recommended that HPV DNA testing be used as a triage test for patients whose Pap smear results are classified as ASC-US.
In the case where a liquid-based Pap smear has been performed, the same sample used to perform the Pap smear analysis can be conveniently used to perform a “reflexive” HPV DNA test, thereby obviating the need for a repeat clinic visit and second Pap smear. In this case, if a slide is positive for ASC-US, an aliquot (e.g., 4 mL) of the fluid sample is removed from the stored vial and sent to a molecular diagnostic laboratory for HPV DNA testing.
Significantly, laboratories that perform HPV DNA tests are weary of molecular contamination—a well-known problem in molecular diagnostic laboratories. Thus, due to the risk of cross-contamination, molecular diagnostic laboratories may not accept aliquots that have been taken from an already processed liquid-based Pap smear for fear of unnecessarily generating false HPV positives.